With the increasing demand for automotive electronic components year by year, a variety of driving information display devices have been developed successively. In general, driving information display devices are usually disposed on a dashboard, but driving accidents are likely to be caused while a driver looks down at the information on the dashboard. Therefore, head-up displays that can display driving information on a windshield have been widely used. Since the head-up display can reduce the number of times and the time that the driver's line of sight leaves the front field of view, driving safety can be further protected.
In general, the head-up display projects an image beam to a projection screen with an image projection component for display. The projection screen may be a windshield of a vehicle, a reflective film affixed on a windshield, or an independent reflective plate, etc. However, in the daytime or when an ambient light source is stronger, the contrast of the images displayed on the projection screens is caused to be too low, resulting in difficulties in reading.